There exist content recommendation systems capable of searching delivered contents for those matching a user's preferences and providing the user with information about the contents thus detected (one such system is disclosed in Japanese Patent Laid-open No. 2000-287189).
The above type of system typically checks the contents for attributes that have been frequently selected by the user (e.g., one such attribute is the genre of contents), and recommends contents according to each attribute deemed to match the user's preferences.
However, the attributes of contents are generally established by their providers based on in-house content organizations and other circumstances specific to the providers. As a result, these attributes are often inappropriate as the basis for detecting efficiently or effectively the contents that may be recommended.